1. Field of the Invention
The present invention relates to a support structure for supporting a plurality of components forming a part of an electronic apparatus and to a support structure which is combined with other support structures to complete the electronic apparatus. For example, the present invention relates to a support structure in an image forming apparatus such as a digital copier or optical printer, which support structure is completed by combining a plurality of square bodies which are realized by square pipes, and supports each of components as described above so as to maintain a predetermined positional relationship between them, namely, positional accuracy, and as well which is combined with other support structures while the positional relationship between the components being maintained.
2. Description of the Related Art
A support structure, namely, housing structure, commonly used in an image forming apparatus is a support structure which holds components including units, which components form an image forming apparatus between front and rear frames fabricated by punching metal sheets through press processing. Another means for forming a support structure is to perform integral molding of a resin to form a housing, namely frames in which each component is positioned.
However, the former configuration of a support structure is likely to cause deflection, in other words, distortion, of the front and rear metal sheet frames that form the housing of the support frame in the case of a large-sized apparatus, which makes it impossible to maintain the positional accuracy between the components. For example, in the case of an image forming apparatus in which the surface of a photosensitive body is irradiated by laser light to optically scan the same, even if the unit for laser beam irradiation and the photosensitive body are supported so that their positional accuracy is maintained, distortion or the like associated with the strength of the frames makes it impossible to maintain the positional accuracy.
As the processing speed of an apparatus increases, the front and rear frames serving as a housing of the support frame become more liable to distortions, which makes it impossible to maintain the positional accuracy between the components as described above. Vibration occurs at the main body of the apparatus in relation to the strength of the frames just as described above, which causes deviations and consequently a reduction in image quality.
With the latter configuration of a support structure, positional accuracy between components can be maintained to some degree. However, the method based on integral molding of resin is limited by the size of the housing, namely, frames, with respect to the method and cost for manufacturing the same. Therefore, this method will have some limitation when applied to large or high speed processing apparatuses.
Under such circumstances, products have recently been marketed which are support structures in the form of frames completed by welding square hollow pipes and configured to support various components in a space maintained by the support structure.
With this configuration, since the support structure is formed by square pipes as a frame, the strength of the support structure can be maintained even in a large apparatus, which is significantly advantageous in that working of mounting components can be simplified.
For example, Japanese Unexamined Patent Publications JP-A 63-188160 (1988) and JP-A 3-33762 (1991) disclose configurations in which square hollow pipes as frames form a support structure as described above and in which various components forming an electronic photocopier are supported in spaces maintained by the structure.
An image forming apparatus includes a scanner for reading images. Such a scanner includes means for optically scanning an original document for reading an original document image, and beams from the image obtained by the scanning means are projected, for example, upon a photosensitive body or the like which is a recording medium or projected upon a reading device such as a CCD. Therefore, a similar support structure is fabricated to support various components constituting a scanner including the scanning means in a space by the support structure.
In the above-described scanner, the scanning means for optically scanning an original document must be supported with improved positional accuracy, and the positional accuracy can be maintained by providing a support structure constituted by square hollow pipes as described above.
Digitalization is recently being accelerated in the market of copiers, while increasing in size and speed being accelerated in the market of printers. Matters of concern under such circumstances are positional accuracy between various components which form electronic apparatuses such as copiers and printers and reduction of vibration and distortion of the body of the apparatuses themselves. If such problems can not be solved, the quality of an image reproduced and outputted by an image forming apparatus will be adversely affected. As a result, the strength of a support structure for supporting various components constituting each copier or printer becomes significantly important.
A support structure of metal sheet frame has problems with mechanical strength, deviations and the like as described above, whereas integrally molded resin frames have problems in size and cost.
When image forming apparatuses are introduced onto the market, it is necessary to provide a line of apparatuses which can respond to any need of the market. When an apparatus is provided as a structure supported by square pipes as a whole, the basic configuration of the apparatus is fixed. In image forming apparatuses, an image forming portion and a sheet supply portion for supplying sheets as a recording material in various sizes are provided such that they can be separated from each other. According to the disclosure of techniques for support structures in the above-cited patent publications, however, an image forming portion and a sheet supply portion can not be separated from each other because of the integral structure.
A digital copier can substantially be provided by combining a printer and a scanner, however, if the printer and scanner are supported by an integrated support structure for this purpose, they can not be separated as individual apparatuses as described above. Accordingly it is necessary to prepare a separate support structure to be exclusively used for them.
As described above, when an apparatus is to be introduced onto the market which has a main body composed of individual units which can be separated for respective functions for responding to various needs of the market, an integral configuration type support structure can not fulfill the requirement, for example, such a structure can not respond to image processing in various sizes of sheets using an image forming portion including a portion for supplying at least sheets in one size and a separate portion for supplying sheets in another size to be used in combination as needed.
A printer as an image forming apparatus can be configured as a copier by attaching a scanner thereto, and the positional accuracy of the scanner and printer can be improved by supporting both of them by a single support structure. However, in order to singly use them as a printer or as a scanner, it is necessary to provide separate support structures.